Effective extraction of heat produced by electrical devices is important in order to extend the useful life of these devices. Conventional heat sink devices typically utilize an array of extended surfaces, such as fins, integrally formed on a common base and projecting into the ambient fluid surrounding the device. The base is placed in thermally intimate contact with a heat-producing device to provide a conduction path to the fin array. Fluid circulation, through forced or natural convection, around the fin array acts as the heat transfer medium to cool the device to a satisfactory operating temperature.
It is well recognized that various design parameters including fin geometry (such as the number of fins, fin spacing, length and width), material selection, device characteristics, and ambient conditions, among others, influence the heat dissipation performance of the heat sink. In some applications, a plurality of fins arranged with predetermined dimensions, or channel width between adjacent fins gives optimum heat sink performance. Such narrow channel heat sinks are described in a pending United States Patent Application by Azar.
Unfortunately, conventional heat sinks are often expensive and difficult to fabricate, particularly in those cases where high heat dissipation performance is required and a plurality of long fins in a close packed array is used in the heat sink design. Known heat sink manufacturing techniques including casting and machining are often ill-suited to produce such high performance heat sinks in a cost effective manner. More specifically, difficulties are common in completely filling the deep cavities necessitated by long fin designs during the casting process. Moreover, the draft angle imposed on the fin geometry to produce acceptable cast parts is often incompatible with narrow channel heat sink designs. Machining, likewise, has limitations in regard to both producing long fin lengths and narrow channel spacing. Lengthy production times, and inefficient material usage also lead to high costs of parts for many machined heat sink designs. More importantly, conventional casting and machining techniques are sometimes incapable of producing the desired heat sink design at any cost.
Fabricated heat sinks may be advantageously employed in applications where other manufacturing techniques are impractical or too costly. Fabricated heat sinks are non-unitary designs in that the base and fin array are manufactured as separate parts, and are then joined to produce the final heat sinks device, using for example, brazing, welding, friction welding, bonding, soldering, and other known techniques. Fabricated heat sinks may be designed to have substantially identical thermal performance as unitary heat sink devices as a result of improvements in both material and fabrication techniques. Any inherent resistance to thermal conduction at the interface between fin field and base of the fabricated heat sink may be both minimized and offset by careful selection of other design parameters. However, while satisfactory in many heat sink applications, including high-performance applications, conventional fabricated heat sinks can be time-consuming to produce as each individual fin needs to be assembled to the base while maintaining often exacting channel spacing.
What is desirable then is a method for fabricating a low-cost heat sink that is suited to a variety of heat-dissipation applications, including high-performance and narrow-channel applications, but is not restricted to a narrow selection of design parameters as is the case with heat sinks produced by conventional manufacturing techniques.